Abstract
New Magnetospheric Multiscale (MMS) observations of small‐scale (~7 ion inertial length radius) flux transfer events (FTEs) at the dayside magnetopause are reported. The 10 km MMS tetrahedron size enables their structure and properties to be calculated using a variety of multispacecraft techniques, allowing them to be identified as flux ropes, whose flux content is small (~22 kWb). The current density, calculated using plasma and magnetic field measurements independently, is found to be filamentary. Intercomparison of the plasma moments with electric and magnetic field measurements reveals structured non‐frozen‐in ion behavior. The data are further compared with a particle‐in‐cell simulation. It is concluded that these small‐scale flux ropes, which are not seen to be growing, represent a distinct class of FTE which is generated on the magnetopause by secondary reconnection.
Highlights
The dayside magnetopause is an important location for studying magnetic reconnection in situ
The 10 km Magnetospheric Multiscale (MMS) tetrahedron size enables their structure and properties to be calculated using a variety of multispacecraft techniques, allowing them to be identified as flux ropes, whose flux content is small (~22 kWb)
It is concluded that these small-scale flux ropes, which are not seen to be growing, represent a distinct class of flux transfer events (FTEs) which is generated on the magnetopause by secondary reconnection
Summary
The dayside magnetopause is an important location for studying magnetic reconnection in situ. Efforts to understand the physics of magnetopause flux ropes and their internal structure have, to some extent, been somewhat limited by the time resolution of the available measurements, plasma. We present novel measurements from the four-spacecraft Magnetospheric Multiscale (MMS) mission [Burch et al, 2015] of two flux ropes observed sequentially in a magnetopause reconnection jet. These flux ropes are small (radius ~ 7 magnetosheath ion inertial lengths (di) ~ 0.17 RE) with duration of a few seconds in the data. The MMS tetrahedron was at 10 km (~0.14di) scale, and the multipoint observations are used, in combination with computer simulation, to study their size, current density filamentation and structure, and nonideal plasma behavior
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